Circuit breaker

ABSTRACT

A circuit breaker for interrupting a direct current, in particular in a power supply system in a vehicle having a main current path that includes a switch, and having a reed relay for detecting an electric current flow across the main current path. The switch is coupled to the reed relay. Also, a use of a circuit breaker is provided.

This nonprovisional application is a continuation of InternationalApplication No. PCT/EP2016/061299, which was filed on May 19, 2016, andwhich claims priority to German Patent Application No. 10 2015 214966.8, which was filed in Germany on Aug. 5, 2015, and which are bothherein incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a circuit breaker for interrupting adirect current, comprising a main current path that includes a switch.The circuit breaker can be a component of an on-board electrical systemof a vehicle, such as a motor vehicle or an aircraft. The inventionfurther relates to the use of a circuit breaker for protecting anon-board electrical system of a vehicle.

Description of the Background Art

Photovoltaic systems usually have a number of photovoltaic modules,which are electrically connected in series or in parallel to each other.The combination of the photovoltaic modules themselves is contacted bymeans of a power line to an inverter, by means of which the electricalenergy provided by the photovoltaic modules is fed into a supplynetwork, which typically has an alternating current. In contrast, adirect current is conducted in the power line as a matter of principle.In order to disconnect the photovoltaic modules from the inverter in theevent of a fault, circuit breakers are normally used by means of whichdamage to the inverter or burn-up of the photovoltaic modules due to anexisting electric current flow is prevented. In this case, electriccurrents with a current strength of several 10 amperes are usuallyswitched, wherein an electrical voltage of several 100 volts is presentat the contacts between the individual electrical poles due to asuitable interconnection within the photovoltaic module.

A further application for circuit breakers for interrupting a directcurrent are vehicles, such as aircraft or motor vehicles. In this case,motor vehicles which are driven by an electric motor usually have ahigh-voltage on-board electrical system which comprises a high-voltagebattery. An electrical voltage between 400 and 500 volts and a currentstrength of up to several 100 amperes is provided by the high-voltagebattery. In the event of a malfunction of the high-voltage battery or ashort circuit within the inverter or electric motor connected thereto,the quickest possible disconnection of the high-voltage on-boardelectrical system is required for safety reasons. To avoid burn-up ofthe high-voltage battery, the shortest possible switching time isrequired. This is also to be ensured in the case of a motor vehicleaccident and a short circuit caused thereby within the electric motor orinverter, wherein, depending on the type of accident, failure of a powersupply of the circuit breaker cannot be excluded.

A further challenge is the detection of the overcurrent itself, becausedue to the direct current a transformer coupling by means of coilscannot be used for detecting the current strength. Usually, therefore,bimetallic sensors or impact armature systems are used, which have anelectric coil through which the electric current flows. In this case,however, losses arise within the electric coil, which, on the one hand,reduces the efficiency and, on the other, results in the heating of thecircuit breaker, which must be adjusted to this heat input. Theproduction costs are increased because of the cooling elements thusrequired. An alternative to this is the use of a shunt, in which thedropping electrical voltage across a certain line section whoseelectrical resistance is known is detected. The electric current flow iscalculated on the basis of the detected electrical voltage. Thedisadvantage here is that the electrical resistance itself istemperature-dependent, which leads to a faulty value for the currentstrength. Alternatively, a material with a substantiallytemperature-independent electrical resistance is selected for the shunt,which increases the manufacturing costs, however.

In all circuit breakers, the sensors are always electrically contactedto the line, which leads to the electric current flow to be interrupted,so that the circuit breaker itself must be electrically isolated fromother components. It is also necessary to take appropriate measureswithin the circuit breaker against an unintentional short circuit withinthe circuit breaker, which would otherwise lead to a continuation of thecurrent flow and consequently to the functional loss of the circuitbreaker.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide. aparticularly suitable circuit breaker for interrupting a direct current,wherein safety is increased in particular and manufacturing costs arepreferably reduced. A further object of the invention is to provide forthe use of a circuit breaker.

The circuit breaker is used for interrupting a direct current and isparticularly suitable for interrupting a direct current. The circuitbreaker is preferably provided and configured for interrupting a directcurrent. The circuit breaker is electrically contacted, for example, bymeans of a photovoltaic system or a photovoltaic module and, forexample, a component of a photovoltaic system or a photovoltaic powerplant. In an alternative to this, the circuit breaker is a component ofan on-board electrical system of a vehicle, for example, a high-voltageon-board electrical system, which has an electrical voltage greater than100 volts, 200 volts, 300 volts, or 400 volts and, for example, lessthan 1000 volts or 900 volts. The vehicle is, for example, an aircraftand the on-board electrical system serves, for example, to supply theactuators of the aircraft. In an alternative to this, the vehicle is amotor vehicle, in particular an electric or hybrid vehicle. Inparticular, in this case, the circuit breaker is a component of theon-board electrical system, which serves to supply current to a maindrive of the motor vehicle.

The circuit breaker is provided in particular to switch electriccurrents greater than or equal to 10 amperes, 100 amperes, 200 amperes,300 amperes, 500 amperes, or 600 amperes. Expediently, the maximumcurrent strength switchable with the circuit breaker is 900 amperes,1000 amperes, 1500 amperes, or 2000 amperes. For example, the electricalvoltage switchable with the circuit breaker is greater than 10 volts, 50volts, 100 volts, or 200 volts. In particular, the switchable electricalvoltage is less than 500 volts, 600 volts, 700 volts, or 1000 volts.

The circuit breaker has a main current path, which conducts the directcurrent to be interrupted during operation. The main current pathcomprises a switch, by which when it is actuated the current flow isinterrupted. For this purpose, the switch preferably comprises twocontacts, which can be taken by means of suitable control of the switchfrom an electrically conductive to an electrically non-conductive state.In other words, the two contacts are electrically conductively connectedto one another or electrically insulated from one another, whereinexpediently the switching operations are reversible. The switchexpediently has further components, which are not part of the maincurrent path and by means of which an activation takes place, so thatthe current flow is influenced via the main current path. The switch is,for example, a semiconductor switch, in particular a power semiconductorswitch, such as a GTO or a MOSFET. In an alternative, the switch is anelectromechanical switch, such as a relay, or has a number of switchingelements of this type, such as, for example, a semiconductor switch andan electromechanical switch, which are connected in parallel or inseries to one another. For example, the switch comprises twoseries-connected electromechanical switches or a contactor in adouble-break configuration.

The circuit breaker further comprises a reed relay for detecting theelectric current flow conducted across the main current path. In otherwords, the reed relay is provided and configured to detect the electriccurrent flow across the main current path. Relays of this kind arerelatively inexpensive to produce, which is why the manufacturing costof the circuit breaker is reduced. The reed relay, also referred to as areed switch or reed contact, preferably has a glass tube with fusedcontact blades made of a ferromagnetic material. The contact blades arein particular made of an iron-nickel alloy and are provided andconfigured to move relative to one another as a function of an externalmagnetic field, wherein at a certain magnetic field strength, the twocontacts are electrically contacted to one another. At a furtherpredetermined magnetic field strength, the two contacts are electricallyisolated from one another, expediently spaced apart from one another. Inparticular, the two contacts are disposed within a container, such as atube, preferably a glass tube, which is expediently filled with aprotective gas, for example nitrogen/hydrogen, or with an inert gas.Alternatively, the housing is evacuated.

The switch is coupled to the reed relay, for example, in terms ofsignaling or electrically. In particular, the reed relay is disposedsuch that the switching state of the switch is changed as a function ofa signal detected by the reed relay. Expediently, the reed relay isdisposed such that in the case of an overcurrent the main current pathchanges the switching state of the reed relay.

In this case, no direct electrical contact with the main current path isrequired for detecting the current flow, which is why the reed relay ispreferably galvanically isolated from the main current path, so that ashort circuit of the circuit breaker due to the reed relay can besubstantially ruled out. In addition, no electric current is requiredfor operating the reed relay, so that, on the one hand, it requires noelectrical energy for operation. On the other hand, it is also notheated during operation, so that no relatively complex design measuresfor its cooling need to be taken. Further, detection of a change in theelectric current flow takes place within a relatively short time, whichis why the circuit breaker has a relatively short trippingcharacteristic, so that safety is increased.

The switch can have an electromechanical switch or is formed by it.Here, the switch contacts are moved by an electromagnetic coil, which issuitably connected to one of the switch contacts. The reed relay ispreferably electrically contacted to the electric coil of the switch,for example, directly or by means of other electrical components. Forexample, the reed relay is connected in parallel to the electric coil.Particularly preferably, however, the reed relay is connected in seriesto the electric coil of the switch, so that the energization of theelectric coil is changed upon a change in the switching state of thereed relay. For example, only one electric line or further electricalcomponents are connected hereby between the reed relay and the electriccoil. Due to the series connection, thus substantially immediately aftera change in the electric current flow across the main current path andconsequently switching of the reed relay, switching of the switch by itselectric coil is enabled, which is why the switching time of the circuitbreaker is shortened further and safety is increased.

For example, the reed relay can be designed in the manner of asingle-pole switch, by means of which only an electric current flow isswitched on or off. In this way, a relatively robust circuit breaker isprovided whose manufacturing costs are relatively low. Consequently,upon actuation of the reed relay either the electric coil of the switchis energized or its energization is interrupted. Consequently, aswitching operation is carried out by means of the switch, if aswitching operation is performed by the reed relay. Particularlypreferably, however, the reed relay has a changeover switchconfiguration which comprises a center terminal and a first and secondterminal, wherein, depending on the switching state of the reed relay,the center terminal is electrically contacted either to the firstterminal or to the second terminal. In this case, for example, the firstterminal is normally electrically contacted to the center terminal, andthe center terminal is electrically isolated from the second terminal.In other words, the first terminal is “normally closed” (NC) and thesecond terminal is “normally open” (NO). In particular, the reed relayis a monostable changeover contact or at least constructed in the mannerof a monostable changeover contact. In an alternative, the reed relay isa bistable changeover contact or at least constructed in the manner of abistable changeover contact.

The center terminal can be electrically contacted to the electric coilof the switch, so that, depending on the switching state, it iselectrically contacted either to the first or second terminal. Forexample, the center terminal is contacted directly to the electric coilor further electrical components of the circuit breaker are locatedbetween them and these are thus connected in series to the centerterminal and to the electric coil. At least, however, there are nofurther components of the reed relay between the center terminal and theelectric coil. In particular, the switch is in the electricallyconductive state only when the electric coil is energized, thus conductscurrent. Consequently, in a switching operation of the reed relay, theelectrical energy stored in the coil is dissipated by a current flow tothe second terminal, and therefore the switching time is furthershortened.

Expediently, for this purpose, a first capacitor can be connected inparallel to the electric coil and the reed relay. In particular, thefirst capacitor is electrically contacted to the second terminal of thereed relay, which is electrically isolated from the center terminal inthe normal state. Consequently, in the case of a reed relay switch, aresonant circuit is formed by means of the first capacitor and theelectric coil of the switch, a circuit by means of which the electricalenergy stored in the electric coil is dissipated. Expediently, the firstcapacitor is not charged when the circuit breaker is in the electricallyconductive state (normal state), which is why, on the one hand, apossible operating time of the first capacitor is increased and, on theother, the possibility of an electrical short circuit is prevented.

A diode, for example two diodes, can be connected between the firstcapacitor and the electric coil. wherein one of the diodes, whoseconducting direction is preferably directed in the same direction, isexpediently arranged here between each electrode of the first capacitorand the electric coil. Consequently, in a switching operation of thereed relay, a single oscillation operation is carried out in which dueto the inductance of the electric coil its stored electrical energy issubstantially completely charged to the first capacitor. Discharging ofthe first capacitor is prevented due to the diode, which is why arenewed energization of the electric coil can be excluded, which wouldlead to unintentional reclosing of the switch.

The circuit breaker can comprise a drive coil, therefore, a furtherelectric coil. The drive coil is coupled to the first capacitor. Inparticular, the drive coil is energized by the first capacitor.Preferably, a diode is connected in series to the drive coil, said diodeby means of which dissipation of the electrical energy, transmitted tothe drive coil, back to the first capacitor is prevented. Expediently,the drive coil is electrically contacted to a second capacitor. Forexample, the drive coil is connected in parallel to the secondcapacitor. Suitably, however, the second capacitor is connected inseries to the drive coil, so that energization of the drive coil occursor can at least occur by means of the second capacitor. For example, thesecond capacitor is electrically contacted to the first capacitor orconnected thereto in terms of signaling. Expediently, the two capacitorsare connected in such a way that when the charge state of the firstcapacitor changes, the drive coil is energized or at least anenergization of the drive coil is changed. Consequently, in a switchingoperation of the reed relay, the energization of the drive coil ischanged and/or in particular the state of charge of the secondcapacitor. Due to the drive coil, a discharge of the first capacitor ismade possible, so that after the tripping of the circuit breaker, theelectrical energy stored in the first capacitor is dissipated, whichincreases safety. In particular, a component is driven by means of thedrive coil and thus the energy stored in the drive coil is dissipated.

Suitably, the drive coil can be electrically contacted to the secondcapacitor by means of a switching element. In other words, the switchingelement is located between the second capacitor and the drive coil. Forexample, the switching element is a semiconductor switch, in particulara thyristor. The gate of the semiconductor switch is preferably coupledto the first capacitor, for example, electrically or in terms ofsignaling, so that when the state of charge changes, the switchingelement switches, so that the drive coil is energized by the secondcapacitor. In other words, the drive coil is coupled to the firstcapacitor by the thyristor. Expediently, in the normal state, therefore,when the circuit breaker is in the electrically conductive state, thesecond capacitor is charged so that, when the state of charge of thefirst capacitor is exceeded above a threshold predetermined by thethyristor within a relatively short period of time, the drive coil isenergized with a relatively large electric current flow.

In an embodiment of the invention, the drive coil is coupled to thefirst capacitor by means of a coupler. In particular, the coupler is agalvanically isolating coupler, so that the drive coil is galvanicallyisolated from the first capacitor and thus also from the reed relay. Forexample, during operation, a pulse transfer is made possible by means ofthe coupler despite galvanic isolation. Expediently, the coupler is atransformer or in particular an optocoupler, which has on the input sidein particular a light-emitting diode (LED) and/or on the output side aphotodiode, a phototransistor, and/or a DIAC.

Expediently, in this case, the second capacitor can be electricallycontacted to the main current path. In particular, an electrode of thesecond capacitor is electrically contacted directly to the main currentpath, in particular to one of the terminals of the circuit breaker.Preferably, the second electrode of the second capacitor is electricallycontacted to a further terminal of the circuit breaker, for example,directly or by means of further components. Expediently, duringoperation of the circuit breaker, the electrical voltage of the on-boardelectrical system is applied at the second capacitor, if the circuitbreaker is a part of the on-board electrical system. The secondcapacitor in particular is suitably placed for this purpose. As aresult, during operation a relatively large amount of electrical energyis stored by the second capacitor, so that when the reed relay isswitched, not only the energy stored in the electric coil of the switchand transmitted by means of the first capacitor to the drive coil, butan amount of energy increased in contrast thereto is available forenergizing the drive coil, which is why any component driven by thedrive coil is accelerated relatively quickly. Due to the coupler, inthis case, the second capacitor is galvanically isolated from the reedrelay, which increases safety.

The coupler can be electrically contacted to the switching element, inparticular to the gate of the semiconductor switch, in particular thethyristor, if these are present, so that the coupling between the drivecoil and the coupler is created by means of the thyristor. Expediently,the coupler is connected in parallel to the first capacitor.

In particular, one electrode of the second capacitor is electricallycontacted to the main current path by means of a third capacitor. Inother words, the second and third capacitors are connected in series,wherein the third capacitor is placed between the second capacitor andthe main current path. In this way, a galvanic isolation is realizedbetween the second capacitor and the main current path, which furtherincreases safety. In addition, not all of the electrical voltage appliedto the main current path is applied to the second capacitor, which iswhy it can be made smaller, which reduces manufacturing costs. In analternative to this, another galvanic decoupling between the secondcapacitor and the main current path is used.

In an embodiment, the coupling of the drive coil to the first capacitoris effected by means of an electrical parallel connection. In otherwords, the drive coil is connected in parallel to the first capacitorand electrically contacted to it. In this case, preferably, theswitching element or a further switching element is connected in seriesto the drive coil, so that by actuating the switching element, such as asemiconductor switch, such as, e.g., a transistor or a thyristor, thedrive coil is energized by means of the first capacitor. In this way,the electrical energy stored in the first capacitor is dissipated by thedrive coil. In particular, in this case, the second capacitor, if it ispresent, is connected in parallel to the first capacitor, whereinexpediently a current flow from the second capacitor to the firstcapacitor is prevented by a diode.

For example, the circuit breaker comprises a secondary current path thathas the reed relay and the electric coil of the switch. If the circuitbreaker is a component of the on-board electrical system of the motorvehicle, a high-voltage on-board electrical system of the motor vehicleis expediently safeguarded by means of the main current path. Thesecondary current path here is preferably a component of a low-voltageon-board electrical system which has, for example, 12 volts, 24 volts,or 42 volts. In particular, the electrical voltage and/or the electriccurrent of the secondary current path is less than the respectivecorresponding value of the main current path. As a result, the currentflow conducted by the switch but not by the electric coil of the switchis interrupted. Consequently, during operation, the electric coil of theswitch and the reed relay conduct relatively low electricalvoltages/electric currents, wherein relatively large electriccurrents/electrical voltages conducted by the main current path can beswitched by the circuit breaker.

In an embodiment of the invention, the circuit breaker comprises acontrol unit, which is created, for example, by means of electricaland/or electronic components. For example, the control unit comprises amicroprocessor. The reed sensor (reed relay) is coupled in terms ofsignaling to the control unit, which in turn is connected to the switchin terms of signaling. Consequently, when a fault is detected, a signalis first transmitted by the reed switch (reed relay) to the control unitand is evaluated by the control unit. If the electric current flowdetected by the reed relay exceeds a threshold value, a control signalfor the switch is created by the control unit, so that the main currentpath is electrically interrupted. The switch in this case is, forexample, a semiconductor switch whose gate is electrically contacted,for example, to the control unit. For example, the semiconductor switchis a power semiconductor switch, such as a GTO or MOSFET. Alternatively,the switch is an electromechanical switch, such as a relay or has anumber of switching elements of this type, such as, for example, asemiconductor switch and an electromechanical switch, which areconnected in parallel or in series. For example, the switch comprisestwo series-connected electromechanical switches or a contactor in adouble-break configuration. The control unit expediently comprises anenergy storage, for example, a battery or a capacitor, so thatmonitoring is made possible even if the external power supply for thecontrol unit fails at least for a certain period of time.

The switch can have an armature which is at least partially disposedwithin the electric coil. The armature is mechanically coupled to atleast one of the switch contacts of the switch, in particular connectedto them, preferably attached thereto. If the energization of theelectric coil changes, consequently the armature is moved within theelectric coil. For example, the armature and/or the switch contact isspring-loaded. The spring force is canceled by the magnetic force, whichis provided by the electric coil, if it is energized. Consequently, inthe event of an interruption in the energization of the electric coil,the switch contact is moved on account of the acting spring force, sothat the switch is brought into an open state. Safety is increased inthis way.

Expediently, an auxiliary drive is coupled to the armature. Theauxiliary drive is expediently activated only if the reed relay isswitched. Consequently, in the event of a fault/overcurrent, thearmature is moved relatively quickly, so that a switching time of thecircuit breaker is shortened. Expediently, the drive coil is a componentof the auxiliary drive, provided that the drive coil is present.Consequently, the electrical energy stored in the electric coil isdissipated by means of the auxiliary drive. Consequently, the armatureis accelerated due to the electrical energy already stored in thecircuit breaker. Particularly preferably, in this case the secondcapacitor is present, so that a force applied by the auxiliary drive isrelatively large.

Expediently, the auxiliary drive comprises an eddy current drive. Theeddy current drive has a second electric coil, against which anelectrical conductor expediently bears mechanically in the electricallyconductive state of the circuit breaker, an insulation layer preferablybeing located between these. The electrical conductor is expedientlycoupled to the armature or coupled by means of a further element. Whenthe second electric coil is energized, which is in particular the drivecoil, the electrical conductor itself is therefore repelled from thesecond electric coil due to the inhomogeneity of the magnetic fieldduring its generation and the thus induced eddy currents within theelectrical conductor. Here, for example, the electrical conductor,hereinafter also referred to as the actuating element, is mechanicallycoupled directly to the armature, so that the auxiliary drive actsdirectly on the armature.

In an alternative to this, the auxiliary drive comprises a mechanicalspring element, which is connected to the armature by means of aflexible connecting element. The connecting element is, for example, asteel band or made of a rubber, a cord, or the like. Consequently, theauxiliary drive only enables a force exerted in one direction, which iswhy the armature can be switched without operating the auxiliary drive.Expediently, a mechanical spring element, such as a coil spring or acoiled torsion spring, is connected to the connecting element. Thespring element is held in a tensioned state, for example, by means oflatching, in particular with the actuating element of the eddy currentdrive, if it is present. When the auxiliary drive is triggered, thelatching is consequently released and the armature is accelerated by thespring element via the connecting element. Expediently, the mechanicalspring element is tensioned, if the latching exists. In other words,mechanical energy is stored in the mechanical spring element.Consequently, even when the auxiliary drive is energized with arelatively low energy, a relatively large exertion of force on thearmature is made possible, for which purpose the mechanical springelement is pretensioned during assembly.

Expediently, the main current path comprises a busbar, which isproduced, for example, by means of a copper bar. The busbar isexpediently electrically isolated on the outside, which prevents a shortcircuit. The busbar is peripherally surrounded at least in sections by acarrier, which in particular bears against the busbar in a positivemanner. The carrier is expediently made of a ferromagnetic material and,for example, is plugged onto the busbar. Consequently, the magneticfield surrounding the busbar is formed by the carrier. The carrier has arecess within which the reed relay is positioned. The recess isconfigured in particular groove-shaped, wherein the opening of thegroove is expediently closed by means of the busbar. Alternatively, therecess is designed in the manner of a gap, so that the carrier is notformed completely surrounding the busbar due to the gap, but has twoends spaced apart from one another by means of the gap. As a result, thereed relay is penetrated substantially only by the magnetic field lines,which are caused by the electric current flow conducted by the busbar.Consequently, substantially only the magnetic field, generated by theelectric current flow, is detected by the reed relay due to the carriermade of a ferromagnetic material. Further external magnetic fields, incontrast, are detected by the reed relay only to a relatively smallextent, which is why the number of false trips is relatively low.

The reed relay can be held within the recess, wherein an air gap isformed between the carrier and the reed relay. It is made possiblehereby by the air gap to set the current strength of the electriccurrent flow, which is conducted across the main current path and atwhich a switching operation of the reed relay is triggered. In otherwords, by means of the air gap, the strength of the magnetic fieldpenetrating the reed relay is set as a fraction of the magnetic fieldpenetrating the carrier. As a result, an adjustment of the circuitbreaker (trip threshold) is made possible by a change in the carrier, inparticular by means of adjustment of the air gap. Replacement of thereed relay is not required, however. Consequently, in the manufacture ofthe circuit breaker, only a single type of reed relay is needed,regardless of the desired operating condition.

The reed relay can be held within the recess by means of a holder, sothat the air gap is substantially constant even with a vibration of thecircuit breaker. Here, the reed relay is at least partially surroundedpositively and/or frictionally by the holder, which is at leastpartially disposed within the recess. The holder itself is expedientlymade of a paramagnetic or diamagnetic material. In particular, themagnetic permeability of the material of the holder is substantiallybetween 0.9 and 1.1 and expediently substantially equal to 1, so thatthe magnetic field conducted by the carrier is substantially unaffectedby the holder.

To protect an on-board electrical system of a vehicle, such as a motorvehicle or an aircraft, a circuit breaker is used which comprises a maincurrent path that includes a switch and a reed relay for detecting anelectric current flow across the main current path. The switch iscoupled to the reed relay, for example, electrically or in terms ofsignaling. The on-board electrical system is particularly preferably ahigh-voltage on-board electrical system, which conducts an electriccurrent with a current strength greater than 10 amperes, 20 amperes, 50amperes, 100 amperes, or 200 amperes. In particular, the maximumelectric current strength carried by the high-voltage on-boardelectrical system is less than 2000 amperes, 1800 amperes, or 1500amperes. In particular, the electrical voltage of the high-voltageon-board electrical system is greater than 100 volts, 200 volts, 300volts, or 350 volts. Expediently, the electrical voltage of thehigh-voltage on-board electrical system is less than 1000 volts, 800volts, or 600 volts.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes, combinations,and modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, are not limitiveof the present invention, and wherein:

FIG. 1 shows in a schematically simplified form a motor vehicle with ahigh-voltage on-board electrical system having a circuit breaker;

FIG. 2 in a sectional view shows a busbar of the circuit breaker and areed relay for detecting an electric current flow across the busbar,which is disposed in a recess of a carrier;

FIG. 3 is a plan view of the carrier plugged onto the busbar;

FIG. 4 shows an armature, disposed within an electric coil, of a switchof the circuit breaker, which is coupled to a first embodiment of anauxiliary drive;

FIG. 5 schematically shows a further embodiment of the auxiliary drivecoupled to the armature;

FIG. 6 is a block diagram of a first embodiment of the circuit breaker;and

FIGS. 7 to 9 each show as a circuit diagram different versions of thecircuit breaker.

DETAILED DESCRIPTION

If individual components are referred to as the first, second, third, .. . component, this serves in particular only to designate theparticular component. In particular, this does not imply the presence ofa certain number of components.

A motor vehicle 2 with drive wheels 4 and non-driving wheels 6 is shownin a schematically simplified form in FIG. 1. Drive wheels 4 are coupledto an electric motor 8, which has an inverter (not shown in greaterdetail). The current to inverter/electric motor 8 is supplied by ahigh-voltage battery 10, by means of which electrical energy isprovided, wherein an electrical voltage of 400 volts is applied betweenthe two poles of the high-voltage battery. High-voltage battery 10 iscoupled by means of an electric line 11 to inverter/electric motor 8,wherein an electric current flow I of up to 1000 amperes is conducted byelectric line 11. High-voltage battery 10, electric line 11, andinverter/electric motor 8 are components of a high-voltage on-boardelectrical system 12.

To protect high-voltage electrical system 12, it has a circuit breaker14 which triggers in an overcurrent, therefore, at an electric currentflow I that exceeds 1000 amperes and is caused, for example, due to ashort circuit within inverter/electric motor 8, and thereforeelectrically disconnects high-voltage battery 10 from inverter/electricmotor 8. Motor vehicle 2, moreover, has a low-voltage on-boardelectrical system 16 with a low-voltage battery 18, between whoserespective electrical poles an electrical voltage of 12 volts or 48volts is applied. Low-voltage on-board electrical system 16 furthercomprises a number of actuators 20, by means of which adjustment parts,such as, e.g., windows or seats, can be electrically adjusted.

Circuit breaker 14 has a main current path 22 with a busbar 24, which isshown in a cross section in FIG. 2 and in a plan view in FIG. 3. Thesubstantially cuboid busbar 24 has a copper core, therefore, a core madeof a copper, which is surrounded on the outside by an insulating layer26 made of a plastic, so that an electrical short circuit with othercomponents of circuit breaker 14 can be substantially ruled out. Busbar24 is surrounded by a carrier 28, which is also configured substantiallycuboid. Carrier 28 is made of a ferromagnetic material and has a centralopening 30, within which busbar 24 is disposed in a positive manner.Further, carrier 28 comprises a groove-shaped recess 32, runningparallel to busbar 24 and the opening of which is closed by means ofbusbar 24. In other words, recess 32 and opening 30 are connected to oneanother. Within recess 32, a reed relay 34 is disposed, which, however,is spaced apart from carrier 28 to form an air gap 36. In other words,reed relay 34 does not bear against carrier 28. Reed relay 34 is heldwithin recess 32 by means of a holder 38, so that air gap 36 remainseven with vibration of circuit breaker 14. Holder 38 is made of amaterial having a magnetic permeability μ_(r)=1, and is supported at theend, for example, on busbar 24.

Reed relay 34 has a switch contact 42 which is arranged within a glasstube 40 and is electrically contacted to a center terminal 44. Switchcontact 42 is made of a nickel-iron alloy and is pivotable between afirst terminal 46 and a second terminal 48. Glass tube 40 itself isfilled with nitrogen. If there is the electric current flow I andconsequently there is a current flow in a direction 50 that isperpendicular to the cross section shown in FIG. 2, a magnetic fieldforms around busbar 24 and is conducted by carrier 28 through reed relay34. Depending on the strength of the magnetic field, switch contact 42is deflected, so that center terminal 44 is electrically contactedeither to first terminal 46 or second terminal 48. Consequently, reedrelay 34 detects whether electric current flow I exceeds a certainvalue, no electrical energy being needed for the detection, therefore,for the operation of the sensor itself.

FIG. 4 shows a switch 52 of the circuit breaker 14 in detail, which isdesigned in the manner of an electromechanical switch and comprises, forexample, a contact bridge 54 for double interruption (FIGS. 8 and 9).Switch 52 has an electric coil 56, which is shown in a sectional viewalong the longitudinal axis. An armature 58 is positioned within coil56; the armature is made of a ferromagnetic material or a permanentmagnet, which protrudes on the end side with the formation of a couplingpoint 60 of the electric coil and a yoke 62 that surrounds it and ismade of a ferromagnetic material, such as iron, and, for example, ismade of a solid iron core or designed as laminated, therefore, made as alaminated core with sheets electrically isolated from one another, inparticular is made of individual transformer sheets. Contact bridge 54is connected at coupling point 60.

At the opposite end of armature 58, a flexible connecting element 64 isconnected in the form of a steel strip, by means of which an auxiliarydrive 66 is connected to armature 58. Auxiliary drive 66 has amechanical spring element 68 in the form of a spring, to which at theend an end member 70 is connected to which connecting element 64 isattached. A force is exerted by means of mechanical spring element 68 onarmature 58 in an opening direction 72 via connecting element 64. Whenarmature 58 is moved in opening direction 72, the electric current flowI across main current path 22 is interrupted and, for example, contactbridge 54 is moved into an open position.

End element 70 is latched to a holding element 74, so that despite thetensioned mechanical spring element 68, end element 70 remains in apredefined position. Due to the flexible connecting element 64, movementof armature 58 in opening direction 72 for interrupting the flow ofcurrent is made possible, wherein auxiliary drive 66 is not activated.Upon activation of auxiliary drive 66 and release of holding element 64from end member 70 and thus elimination of the latching, armature 58 ismoved in opening direction 72, however, due to connecting element 64,wherein mechanical spring element 68 is relaxed. Holding element 74 ispressed by means of a second mechanical spring element 76 against endmember 70 and the recess formed there, so that the latching exists.

An eddy current drive 78 with a drive coil 80 and an actuating element82 is positioned between holding element 74 and second mechanical springelement 76, wherein actuating element 82 is connected at the end tosecond mechanical spring element 76. Actuating element 82 is made of anelectrically conductive material, such as, for example, aluminum and hasa disc-shaped form with, for example, a circular cross section. Uponenergization of drive coil 80, consequently, actuating element 82 ismoved against the spring force of second mechanical spring member 76 andthus holding element 74 is removed from end element 70, which disengagestheir engagement to one another. As a result, due to mechanical springelement 68, end element 70 is moved in opening direction 72 andconsequently armature 58 as well coupled thereto by means of connectingelement 64.

A further embodiment of auxiliary drive 66 is shown in FIG. 5; saiddrive is coupled to armature 58 of switch 52, which, as in the previousembodiment, is disposed within electric coil 56. Electric coil 56 itselfis again surrounded by yoke 62. Armature 58 also has coupling point 60on its one longitudinal side. Connecting element 64, which may bedesigned as flexible or rigid as well, is also attached at the remainingend. Connecting element 64 is connected to actuating element 82 ofauxiliary drive 66, which is designed in principle similar to theprevious exemplary embodiment. Here as well, actuating element 82 isconfigured disc-shaped with a circular cross section and made of aferromagnetic material, such as aluminum. In the closed state of theswitch, actuating element 82 bears loosely against drive coil 80, whichis designed differently from the previous exemplary embodiment for anelectric current with an increased electric current strength, for whichreason drive coil 80 is wound from a relatively thick wire. In addition,drive coil 80 is attached to yoke 62.

When drive coil 80 is energized, actuating element 82 is removedtherefrom, and due to connecting element 64, armature 58 is pulled outof electric coil 56 in opening direction 72. If switch 52 is operated innormal operation, therefore, there is no fault, electric coil 56 isappropriately controlled. In this case, there is no energization ofdrive coil 80, and armature 58 and actuating element 82, if connectingelement 64 is rigid, are moved in opening direction 72 to interrupt theelectric current flow I. If there is a fault, thus, for example, anovercurrent, drive coil 80 is also energized, which increases theacceleration of armature 58 in opening direction 72.

A first embodiment of circuit breaker 14 is shown schematically in ablock diagram in FIG. 6. Circuit breaker 14 has main current path 22,which at each end has a contact terminal 84 for electrically contactinga power line 86 of high-voltage on-board electrical system 12. Maincurrent path 22 has switch 52, so that an electric current flow Ibetween the two contact terminals 84 can be adjusted by switch 52. As aresult, the two contact terminals 84 are either electrically contactedto one another by means of switch 52 or are electrically isolated fromone another. Switch 52 is signal-coupled by means of a first signal line88 to a control unit 90, which has an energy storage 92 in the form of abattery. During operation, battery 92 is charged by the low-voltageon-board electrical system 16. Due to energy storage 92, operation ofcontrol unit 90 and circuit breaker 14 is also possible in the case of amalfunction of low-voltage on-board electrical system 16.

Control unit 90 is further signal-coupled by means of a second signalline 94 to reed relay 34, which is disposed, for example, within carrier28. The electric current flow I is detected by means of reed relay 34and this value is passed to control unit 90 by means of second signalline 94. If the detected value exceeds a certain threshold value, switch52 is triggered by the first signal line 88, so that the electriccurrent flow I between the two contact terminals 84 of circuit breaker14 is prevented. Switch 52 is, for example, an electromechanical switchor a semiconductor switch, such as a power semiconductor switch, suchas, e.g., a MOSFET or GTO. Depending on the configuration of switch 52,an electric current flow or else an electrical voltage is used as thesignal for actuating switch 52 by means of first signal line 88.

A further embodiment of circuit breaker 14, in which switch 52 is againdesigned as an electromechanical switch and thus has electric coil 56,is shown in FIG. 7. Armature 58, to which contact bridge 54 or otherswitch contacts are connected, or with which they are at leastoperatively connected, is disposed in electric coil 56. Switch 52 has acoil resistor R_(s) which is an ohmic resistor and is formed withinswitch 52, for example, because of different materials and connected inseries to electric coil 56. Electric coil 56 is electrically connectedin series to reed relay 34 and electrically contacted directly to centerterminal 44 of reed relay 34. First terminal 46 of reed relay 34 isrouted to a semiconductor switching element 96 in the form of a fieldeffect transistor, specifically, to its drain, and the source of thefield effect transistor is electrically contacted to a second contactterminal 98, by means of which a terminal of circuit breaker 14 isprovided to low-voltage on-board electrical system 16. In this case, afirst Zener diode D_(Z1) is connected in parallel to the field effecttransistor. Second contact terminal 98 is connected to ground GND. Coilresistor R_(s), in contrast, is routed to a third contact terminal 100whose potential is 12 volts and is provided by means of low-voltagebattery 18. Therefore, a secondary current path 102, which has electriccoil 56 and reed relay 34, which are electrically connected in series,is formed between second and third contact terminal 98, 100.

A first diode D1, a first capacitor C1, and a second diode D2, which arein turn connected in series, are connected in parallel to reed relay 34and electric coil 56 and coil resistor R_(s). Here, second diode D2 iselectrically contacted to second terminal 48 of reed relay 34, whereinthe conducting direction is oriented from second terminal 48 in thedirection of first capacitor C1. Drive coil 80 of auxiliary drive 66,which due to the different materials used also has an ohmic resistor inthe form of a drive coil resistor R_(H), is connected in parallel tofirst capacitor C1. Between auxiliary drive 66 and first capacitor C1,on one side, a third diode D3 is electrically contacted to one of theelectrodes of first capacitor C1 and a fourth diode D4 to the remainingelectrode of first capacitor C1.

Auxiliary drive 66 also has a further diode DH which is connected inparallel to drive coil 80 and drive coil resistor R_(H) and whoseconducting direction is directed opposite to that of fourth diode D4 andthird diode D3. A second thyristor T2, the gate of which is electricallycontacted to a series connection comprising a second Zener diode D_(Z2)and a first resistor R1, is connected between third diode D3 and drivecoil resistor R_(H). In particular, there is no further Zener diode, sothat auxiliary drive 66 has only a single Zener diode, namely, secondZener diode D_(Z2). First resistor R1 is electrically contacted to theelectrode of the first capacitor, which is also electrically contactedto second diode D2 and fourth diode D4. A series connection of a fifthdiode D5 and a second capacitor C2 is connected in parallel to theseries connection of drive coil 80 and drive coil resistor R_(H) andsecond thyristor T2, wherein the cathode of fifth diode D5 is routed tothe cathode of the fourth diode.

The electrode of second capacitor C2, said electrode which is contactedto fifth diode D5, is further routed to a cathode of a sixth diode D6,whose anode is electrically contacted via a second resistor R2 to thirdcontact terminal 100. The electrode of second capacitor C2, saidelectrode which is electrically contacted both to second thyristor T2and third diode D3, is routed via a seventh diode D7 to second contactterminal 98, wherein second capacitor C2 is electrically contacted tothe anode of seventh diode D7. Consequently, drive coil 80 iselectrically contacted by means of second thyristor T2, on the one hand,also to second capacitor C2. On the other hand, the drive coil iscoupled to first capacitor C1.

During operation of circuit breaker 14, semiconductor switching element96 is triggered, so that secondary current path 102 conducts current. Asa result, electric coil 56 is energized and the switch contacts ofswitch 52 are closed, which is why main current path 22 is alsoelectrically conductive. As a result, operation of electric motor 8 isenabled. Further, second capacitor C2 is charged via sixth diode D6 andseventh diode D7, so that the electrical voltage of low-voltage on-boardelectrical system 16 is applied to it, in this example, 12 volts. Adischarge of second capacitor C2 is prevented by sixth diode D6. If anovercurrent across main current path 22 is detected by reed relay 34,therefore, if the electric current flow I across main current path 22exceeds a specific threshold value, and consequently the magnetic fieldsurrounding main current path 22 exceeds a certain value, switch contact42 of the reed relay is at a distance from first terminal 46 and iselectrically contacted to second terminal 48. As a result, a currentflow between second and third contact terminal 98, 100 via secondarycurrent path 102 is interrupted. The electrical energy still stored inelectric coil 56 is transmitted to first capacitor C1 via second diodeD2. A return of the energy from first capacitor C1 to coil 56 isprevented due to second diode D2 and first diode D1. As a result, themagnetic field holding armature 58 within electric coil 56 is dissipatedrelatively quickly. Consequently, if armature 58 is held against aspring force by coil 56, armature 58 is moved relatively early on due tothe spring force.

If first capacitor C1 has been charged by electric coil 56, if thevoltage applied to it exceeds a threshold, which is adjustable by firstresistor R1, second Zener diode D_(Z2), third diode D3, and firstcapacitor C1, second thyristor T2 is triggered. Consequently, theelectrical energy stored in first capacitor C1 is dissipated via drivecoil 38, which is consequently energized.

Further, drive coil 80 is energized due to the ignited second thyristorT2 by second capacitor C2, which has a larger stored amount of energycompared with first capacitor C1. A swinging back and consequentlypolarity reversal of drive coil 80 are prevented by fourth diode D4 andfifth diode D5. Due to the energy stored in first capacitor C1 and insecond capacitor C2, a relatively large amount of energy is available todrive coil 80 for operation. Preferably, auxiliary drive 66 isconfigured according to the embodiment shown in FIG. 4, in whichtherefore even in the case of a small movement of actuating element 82due to mechanical spring member 68, a relatively large force thatexceeds the force that can be applied by drive coil 80 acts on armature58. Thus, the switching of the switch contacts of switch 52 isaccelerated. As a result, even after a relatively short period of timeafter detection of the overcurrent by reed relay 34, main current path22 is interrupted.

FIG. 8 shows a further embodiment of the circuit breaker according toFIG. 7. Secondary current path 102 with electric coil 56, connected inseries between second contact terminal 98 and third contact terminal100, reed relay 34, and semiconductor switching element 96 are leftunchanged in comparison with the previous embodiment. The contacting ofelectric coil 56 to center terminal 44 and the contacting of firstterminal 46 to semiconductor switching element 96 correspond to theprevious embodiment. Reed relay 34 and coil 56 as well are electricallybridged by first capacitor C1, first diode D1, and second diode D2,wherein the anode of second diode D2 is electrically contacted to secondterminal 48, as in the previous embodiment.

In contrast to the preceding embodiment, third diode D3 and second Zenerdiode D_(Z2), whose anodes are electrically contacted to one another,are connected in parallel to first capacitor C1. The cathode of thirddiode D3 is routed to the anode of first diode D1 and the cathode ofsecond Zener diode D_(Z2) to the cathode of second diode D2.

Circuit breaker 14 further comprises an optocoupler IC1 whoselight-emitting diode 104 is electrically contacted on the cathode sideto the anode of first diode D1 and on the anode side to first resistorR1 and a third Zener diode D_(Z3) to the cathode of second diode D2. Thecathode of second diode D2 and the cathode of third zener diode D_(Z3)are electrically contacted to one another. Consequently, light-emittingdiode 104 of optocoupler IC1 is connected in parallel to first capacitorC1. On the output side, optocoupler IC1 has a DIAC 106, which iselectrically contacted on one side to the gate of a first thyristor T1and via a fourth resistor R4 and a third resistor R3 to the anode offirst thyristor T1. The cathode of first thyristor T1 is electricallycontacted to the gate of second thyristor T2, whose anode in turn iselectrically contacted to auxiliary drive 66 and consequently to drivecoil 80. The interconnection of second thyristor T2 to auxiliary drive66 in this case also corresponds to the previous embodiment. Drive coil80 is further routed both to the fourth and third resistor R4, R3,therefore, by means of third resistor R3 to first thyristor T1 and bymeans of fourth resistor R4 to DIAC 106.

Second capacitor C2 and fifth diode D5 are electrically connected inturn in parallel to auxiliary drive 66 and second thyristor T2, whereinfifth diode D5 and second capacitor C2 are connected in series to oneanother. Also, the two electrodes of second capacitor C2 areelectrically contacted, on the one hand, to seventh diode D7 and, on theother, to sixth diode D6 and second resistor R2. However, these are notrouted to the secondary flow path 102 but to main current path 22,specifically, on both sides of an effective resistor R_(LOAD) ofelectric motor 8, which is therefore monitored by circuit breaker 14. Asa result, during operation the electrical voltage of the high-voltagebattery is present at second capacitor C2, specifically, a positivepotential HV+ and a negative potential HV− of high-voltage battery 10.The electrical voltage formed between the two potentials is 400 volts,so that 400 volts are also applied to second capacitor C2.

During operation of circuit breaker 14, semiconductor switching element96 is actuated such that secondary flow path 102 conducts current. As aresult, electric coil 56 of switch 52 is energized, and contact bridge54 is moved to a closed state, so that the electric current flow I bymeans of main current path 22 is enabled. In this case, electric motor 8is energized and consequently motor vehicle 12 is driven. In this case,second capacitor C2 is always charged to the electrical voltage providedby high-voltage battery 10, so that 400 volts are applied thereto.Discharge is prevented by the current-blocking second thyristor T2 andsixth diode D6. For the planned interruption of the energization ofelectric motor 8, semiconductor switching element 96 is actuated again,for example, so that the flow of current across secondary flow path 102is interrupted, and consequently contact bridge 54 is moved to an openposition and thus the energization of electric motor 8 is interrupted.

If an overcurrent is conducted during operation by main current path 22,reed relay 34 is actuated due to the changed magnetic field andconsequently switch contact 42 is swung to second terminal 48, so thatenergization of electric coil 56 is interrupted. Due to a spring load(not shown), in this case, contact bridge 54, which is coupled toarmature 58, is brought into an open state. Electric coil 56 is in turndischarged to first capacitor C1, so that the bringing of contact bridge54 into the open state is counteracted only by a relatively smallmagnetic force due to the magnetic field generated by electric coil 56.

An overvoltage at the first capacitor C1 is prevented by second Zenerdiode D_(Z2), so that it is protected from destruction. The blockingvoltage of third Zener diode D_(Z3) is less than the Zener voltage ofsecond Zener diode D_(Z2), so that when first capacitor C1 is charged toa certain extent, light-emitting diode 104 of optocoupler IC1 isactivated. As a result, first thyristor T1 ignites, which in turn leadsto the ignition of second thyristor T2. As a result, second capacitor C2is discharged via drive coil 80 of auxiliary drive 66. In summary, drivecoil 80 is coupled to first capacitor C1 by means of the two thyristorsT1 and T2 and optocoupler IC1. Due to the through connection ofthyristor T2, there is a relatively steep current slew rate, so that arelatively large force is exerted by means of auxiliary drive 66. Afterthe finite turn-on time of second thyristor T2 and the discharge ofsecond capacitor C2, the holding current of the two thyristors T1 and T2is not reached, so that they start to block again, which increasessafety. Expediently, the variant shown in FIG. 5 is used as an auxiliarydrive and consequently armature 58 is influenced directly by actuatingelement 82. Due to the relatively large electrical voltage applied tosecond capacitor C2, the force applied by means of eddy current drive 78is sufficient for the relatively fast movement of armature 58.

A further modification of circuit breaker 14 is shown in FIG. 9, whereinthe configuration of main current path 22 and the contacting of maincurrent path 22 to seventh diode D7, on the one hand, and via secondresistor R2 to sixth diode D6, on the other, are left unchanged. Also,secondary current path 102 as well as the parallel connection of firstcapacitor C1, third diode D3, second Zener diode D_(Z2), and optocouplerIC1, which are connected in series to first resistor R1 and third Zenerdiode D_(Z3), are left unchanged. Also, auxiliary drive 66 is configuredaccording to the variant illustrated in FIG. 5 and comprises drive coil80, drive coil resistor R_(H), and the parallel-connected diode ofauxiliary drive DH.

DIAC 106 of optocoupler IC1 is in turn electrically contacted to thegate of first thyristor T1 and via fourth resistor R4 and third resistorR3 to the anode of first thyristor T1. The cathode of first thyristor T1is routed to the gate of second thyristor T2, whose cathode iselectrically contacted to the anode of seventh diode D7. Further, thecathode of second thyristor T2 is electrically contacted both to drivecoil resistor R_(H) and to the cathode of the diode of the auxiliarydrive DH, which is connected in parallel to drive coil resistor R_(H) ofdrive coil 80 and an eighth diode D8 whose cathode is electricallycontacted to the anode of auxiliary resistor DH. Further, an electrodeof second capacitor C2 is electrically contacted to the cathode ofeighth diode D8 and the capacitor's remaining electrode is electricallycontacted to the anode of second thyristor T2 and fourth and thirdresistor R4, R3. Consequently, drive coil 80 is electrically contactedin turn by means of second thyristor T2 to second capacitor C2, anddrive coil 80 is coupled by means of the two thyristors T1, T2 andoptocoupler IC1 to first capacitor C1.

The anode of second thyristor T2 is routed via a ninth diode D9 and athird capacitor C3 to the cathode of sixth diode D6, wherein theblocking direction of ninth diode D9 corresponds to the blockingdirection of sixth diode D6. Consequently, second capacitor C2 isconnected to main current path 22 only by means of third capacitor C3 onone side, so that second capacitor C2 is galvanically isolated from maincurrent path 22. Optionally, second capacitor C2 is bridged by a fifthresistor R5 and/or third capacitor C3 by a sixth resistor R6, each ofwhich have relatively large resistance value.

During operation, semiconductor switching element 96 is actuated inturn, so that coil 56 is energized and consequently switch 52 is broughtinto a current-conducting state. As a result, the electric current flowI across main current path 22 is enabled. By means of main current path22, further, second capacitor C2 is charged via third capacitor C3,wherein the full electrical voltage provided by high-voltage battery 10is not applied at second capacitor C2, but according to the capacitivedivision ratio appears between second capacitor C2 and third capacitorC3. Because a reduced voltage is applied to second capacitor C2,individual components of circuit breaker 14, such as, e.g., secondcapacitor C2, sixth diode D6, second resistor R2, . . . , are designedfor lower power ratings, so that relatively inexpensive components canbe used. Furthermore, second capacitor C2 is galvanically isolated frommain current path 22 by third capacitor C3, so that in the case of ashort circuit or malfunction of second capacitor C2, a short circuit ofthe two poles HV+ and HV− of high-voltage battery 10 does not occur,which could otherwise lead to a burn-up or relatively severe damage tohigh-voltage battery 10.

Upon actuation of reed relay 34, first capacitor C1 is again charged. Ifthis capacitor has a certain state of charge, light-emitting diode 104of opto-coupler IC1 is activated due to third Zener diode D_(Z3), whichis why both first thyristor T1 and second thyristor T2 are triggered.Consequently, second capacitor C2 is discharged via drive coil 80, whichis why actuating element 82 of auxiliary drive 66 is moved away fromdrive coil 80 due to the induced eddy currents, which accelerates anopening movement of contact bridge 54.

The invention is not limited to the exemplary embodiments describedabove. Rather, other variants of the invention can also be derivedherefrom by the skilled artisan, without going beyond the subject of theinvention. Particularly, further all individual features described inrelation to the individual exemplary embodiments can also be combinedwith one another in a different manner, without going beyond the subjectof the invention.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are to beincluded within the scope of the following claims.

What is claimed is:
 1. A circuit breaker for interrupting a directcurrent in an electrical system, comprising: a main current path thatincludes a switch; and a reed relay for detecting an electric currentflow across the main current path, wherein the switch is coupled to thereed relay.
 2. The circuit breaker according to claim 1, wherein thereed relay is electrically connected in series to an electric coil ofthe switch.
 3. The circuit breaker according to claim 2, wherein thereed relay has a changeover switch configuration with a center terminalelectrically contacted to the electric coil of the switch, and a firstcapacitor connected electrically in parallel to the reed relay and theelectric coil, wherein the capacitor is connected in series to a diode.4. The circuit breaker according to claim 3, further comprising a drivecoil electrically contacted to a second capacitor and coupled to thefirst capacitor.
 5. The circuit breaker according to claim 4, whereinthe drive coil is electrically contacted to the second capacitor via athyristor.
 6. The circuit breaker according to claim 4, wherein thedrive coil is coupled to the first capacitor via a coupler or anoptocoupler, and wherein the second capacitor is electrically contactedto the main current path.
 7. The circuit breaker according to claim 6,wherein an electrode of the second capacitor is electrically contactedto the main current path via a third capacitor.
 8. The circuit breakeraccording to claim 4, wherein the drive coil is connected electricallyin parallel to the first capacitor.
 9. The circuit breaker according toclaim 2, further comprising a secondary current path having the reedrelay and the electric coil of the switch.
 10. The circuit breakeraccording to claim 1, wherein the reed relay is coupled in terms ofsignaling to a control unit, which is connected to the switch in termsof signaling, and wherein the reed relay has an energy storage.
 11. Thecircuit breaker according to claim 1, wherein the switch has an armaturewhich is disposed within the electric coil and is coupled to anauxiliary drive which has an eddy current drive.
 12. The circuit breakeraccording to claim 11, wherein the auxiliary drive is connected to thearmature via a flexible connecting element, and wherein the auxiliarydrive has a mechanical spring element.
 13. The circuit breaker accordingto claim 1, wherein the main current path has a busbar which isperipherally surrounded in a positive manner by a carrier having arecess within which the reed relay is positioned.
 14. The circuitbreaker according to claim 13, wherein the reed relay is held within therecess via a holder with the formation of an air gap, and wherein theholder is made of a diamagnetic or paramagnetic material.
 15. Thecircuit breaker according to claim 1, wherein the circuit breakerprotects an on-board electrical system in a vehicle or a high-voltageon-board electrical system.
 16. The circuit breaker according to claim1, wherein the electrical system is an on-board electrical system in avehicle.